There are literally dozens of event management solutions that can do most of what we require, but the field narrows considerably when we consider some of the conference-specific needs, or at least it appears to without further investigation.. The most obvious contenders for consideration are then:
Event management with some the ability to support conferences
Arlo: https://www.arlo.co/
- EventPro: http://www.eventpro.net/index.html
- EventsAir: http://www.eventsair.com/
Specialised conference management, maybe with event management functionality
- Conftool: http://www.conftool.net/en/index.html
- OpenConf: https://www.openconf.com/
Free/open source conference managment
- CMT: https://cmt.research.microsoft.com/cmt/
- COD: http://usecod.com/
- Dryfta: https://dryfta.com/
- Open Conference Systems: https://pkp.sfu.ca/ocs/
- OpenConferenceWare: http://openconferenceware.org/